MRAM is a nonvolatile memory technology that uses magnetic polarization to store data, in contrast to other RAM technologies that use electronic charges to store data. One primary benefit of MRAM is that it retains the stored data in the absence of applied system power, thus, it is a nonvolatile memory. Generally, MRAM includes a large number of magnetic cells formed on a semiconductor substrate, where each cell represents one data bit. Information is written to a cell by changing the magnetization direction of the magnetic free layer within the cell, and a bit is read by measuring the resistance of the cell (low resistance typically represents a “0” bit and high resistance typically represents a “1” bit, or vice versa).
An MRAM device generally includes an array of cells that are interconnected using conductive bit lines, conductive digit lines, and/or local interconnects and the like. Practical MRAM devices are fabricated using known semiconductor process technologies. For example, the bit and digit lines are formed from different metal layers, which are separated by one or more insulating and/or additional metal layers. Conventional fabrication processes allow distinct MRAM devices to be easily fabricated on a substrate.
Smart power integrated circuits are single-chip devices capable of providing operating power in a controlled and intelligent manner. Smart power integrated circuits typically include one or more active circuit components, such as, a power circuit component, an analog control component, and/or a digital logic component. Smart power integrated circuits may also include one or more sensors which can be used to measure or detect physical parameters such as position, motion, force, acceleration, temperature, field, pressure and so forth. Such sensors can be used, for example, to control the output power in response to changing operating conditions. For example, in cell phones, smart power products can be engineered to regulate power consumption, amplify audio signals, and supply power to color screens. In inkjet printers, smart power products can help drive the motors and fire the nozzles for ink delivery. In automobiles, smart power products can help control engine and braking systems, airbag deployments, and seat positioning. Smart power products can also be implemented in a wide variety of other applications.
For integrated circuits (IC's) which implement smart power and magnetoresistive random access memory (MRAM) designs, temperature sensing is an important element of power IC design to protect the circuit, device or system.
FIG. 15 is a simplified schematic cross-sectional representation of a conventional integrated circuit device 1500 implementing a temperature sensor 1502 for sensing temperature. The device consists of a temperature sensor 1502, power source 1504, silicon substrate 1506, an insulating substrate 1508, logic 1514 and a MRAM architecture 1516. Both the temperature sensor 1502 and the power source 1504 are embedded within the silicon substrate 1506 while the insulating substrate 1508 lies above the temperature sensor 1502 and power supply 1504. Existing temperature sensors 1502 for measuring the temperature of a power source 1504 suffer from various limitations. The temperature sensor 102 can be implemented using a junction-based device in which a junction band gap changes with respect to changing temperature. Such p/n junction based sensing devices 1502 consume valuable semiconductor layout area or space. Other limitations of such sensing devices 1502 include, for example, excessive size/weight, inadequate measurement precision, inadequate sensitivity and/or dynamic range, high cost and limited reliability among other limitations.
The miniaturization of many modern applications make it desirable to shrink the physical size of electronic devices, integrate multiple components or devices into a single chip, and/or improve circuit layout efficiency. Ideally, such sensors should be manufactured in a cost effective manner which reduces the additional layout area or space the sensors consumes. It would be desirable to have a semiconductor-based device which includes an MRAM architecture integrated with a smart power architecture including sensor components on a single substrate, particularly where the MRAM architecture and the smart power architecture are fabricated using the same process technology. Thus, there continues to be a need for improved temperature sensors.
Accordingly, it is desirable to provide an improved temperature sensor and method, adaptable for measuring temperature. It is further desirable that the improved temperature sensor and method which generates an electrical signal that can be converted to a temperature of a heat source. It would be desirable to provide temperature sensors that can be easily integrated with semiconductor devices and integrated circuits (e.g., temperature sensors which are compatible with semiconductor device and integrated circuit structures and fabrication methods). For example, it would be very desirable to provide temperature sensors which exhibit precision measurement and improved measurement performance and which can be integrated in a three-dimensional architecture to conserve lay out area and allow for processing in a cost effective manner. Other desirable features and characteristics of the invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.